Update 4/09/15: As of today, the new Contacts Preview sort y last name is actually displaying last name first. As you may have guessed this was a big ongoing complaint of users after the sort functionality came out. Note, although displaying last name, first name in the Frequently Contacted section, this section is still sorted by contact frequency and not by the sort selection chosen.
Update 3/24/15: As of yesterday a new sorting feature has been added to the new Contacts Preview. You can now sort by First or Last Name. Seems more and more Google is listening to user requests.
Recently, Google has started offering a new Contacts Preview page, with lots of feature changed, but with a beautiful Material Design UI. One common complaint I have started to notice on the forums and social media is the lack of changing the sort option. In classic Contacts you have the option to sort by first or last name under the More Menu. This option is glaringly absent in the new contacts preview, which defaults to sorting by first name.
However in there is a field included in both classic and new contact preview that can be added to a contact card that will change how it is sorted. This is not a great workaround for resorting your entire contact list, but it can help you place certain items towards the top of your list for example. In classic contacts the field is called File As, in the new Contacts Preview the field is called "add a name used for sorting". This field is not visible when you first enter a contact card, so you need to show all fields to see it. Just open the contact card, click the pencil to the top right to edit, scroll to the bottom and click on Show All Fields. Now you will see the "add a name used for sorting" field. Type the name you wish to sort by and click save.
If you look at the image below, I have three Test Contacts sorted alphabetically by first name. You will see the first test contact with an profile image moves to the second in the list after changing the add a name used for sorting field.